Technology and Latest Results on Fluidic Assembly of Micro ...

June, 2019 | eLux PROPRIETARY | 1Micro LED Display Conference 2019

Technology and Latest Results onFluidic Assembly of Micro-LEDs

JJ Lee, PhD

President & CEO

June 27, 2019


◼ Fluidic assembly fundamental: self alignment, orientation control

◼ AOI to improve fluidic assembly yield

◼ Mura free micro LED display

◼ Advantage of fluidic assembly

◼ Color micro LED display demonstration

◼ Summary

Outline


Fluidic Assembly

Oscillating flow

▪ Substrate features capture µLEDs at precise positions

▪ Oscillating flow yields many capture attempts

▪ Excess µLED disks are recycled

Good oriented fill with p-GaN up

▪ >99.9% fill

▪ 100% correct alignment

▪ Rate > 50 million µLEDs/hr on 12” toolDark circles are 50 µm diameter µLEDsLight circles are 55 µm diameter wells

Video in separate file


µLED Disc Array Construction

High Brightness µLED Fluidic AssemblyTHV

Disc in well

QD

Well on GlassHarvested µLED

µLED Array

LTPS TFT driven µLED~600,000 µLEDs at 167 ppi

◼ Make µLEDs from commercially available LED wafers

◼ Harvest µLED disks into an ink for fluidic assembly

◼ High speed oriented fluidic assembly to position µLEDs in array

◼ Simple, low cost high volume manufacturing

◼ µLED assembly is the critical processing technology◼ Motion: Distribute µLED over the backplane to trapping points

◼ Trapping: Position and hold the µLED precisely to make array

◼ Orientation: Orient 100% of µLED diodes for forward bias


◼ Primary goal is fill = 1◼ µLEDs move and trap C1 ≠ 0

◼ µLEDs do not detrap C2 = 0

◼ Secondary goals◼ Speed

◼ Utilization

Brief Fundamentals of Fluidic Assembly


In-situ Control of Fluidic Assembly

◼ Full display can be monitored during processing

◼ In-situ tuning of assembly parameters ◼ Improved fill yield and assembly speed

◼ Decrease residual µLEDs on surface

◼ End point control for completed assembly

First assembly yield loss %

Assembly after parameter tuning

9 defects, 2 residual

Automated identification


◼ DSLR image of µLED emission

◼ FOV > 45 cm2 in less than a second

◼ Yield feedback for fabrication

◼ Repair map and Mura correction (next)

µLED Yield Metrology


Dispense

Assembly

Clean-off

Recycling

Brief Process Flow for Fluidic Assembly

Bonding

Metrology

Residual µLEDContaminantsFluidR

emo

ve

Substrate

Passive matrix100% fill

µLED Ink

YieldSpeed

High efficiency and yield

CleanLow loss

TFT Electrode with wells to capture µLEDs

MatureCore techIntegration

Goodcontact


µLED PerformanceHX01 AM

Operation Range

▪ Blue LED wafers by conventional GaN MOCVD process on sapphire

▪ 40 µm diameter planar µLEDs

▪ Harvested by laser lift off

▪ Higher efficiency ~45% with lower droop

▪ Narrow range of electrical properties with Vf at 2.75 V

▪ Performance similar to general lighting LEDs


Rigorous MOCVD Requirements for Conventional Mass Transfer

2

3

4

1 5

Wavelength Variations on an Epi-wafer

▪ Wavelength distribution

▪ Conventional MOCVD has wavelength distribution > 5 nm

▪ Sorting and binning is not suitable for mass transfer technology using for µLED

▪ Current method is to select stamps with proper emission wavelength and discard others

▪ Defect management

▪ Sorting can exclude the defect dies in conventional LED industry because each die is tested

▪ Defective µLED dies can be detected and excluded from transfer

▪ Current strategy is to repair defects on stamp area with good yield, discarding stamps with higher defectivity

▪ Edge exclusion

▪ For faster transfer, large stamp size is preferred, but waste area is large

22 nm

Waste areaoutside stamp


Mura Free µLED Display

2

3

4

1 5

Uniform Color and Luminance Fluidic Assembly

Conventional P&P Mass Transfer

Proprietary Fluidic Assembly

µLEDs in Liquid Fluidic Assembly on TFT Glass

Wavelength & Emission Variations on an Epi-wafer Mosaic and Non-uniform


Comparing to Pick-and-Place Mass Transfer (1/2)

µLED Chip Process

Wafer Bond to Temporary Carrier

Laser Liftoff

COB Process: Pick up and Bond to 2nd

Temporary CarrierTool cost: $2M

COB Transfer to TFT Glass - Group Bonding

Tool cost: $2M

HarvestTool cost: $1K (glass beaker)

Fluidic Assembly and Bonding

Tools cost: $100K

eLux Fluidic AssemblyP-P Mass Transfer P-P Mass Transfer

eLux Fluidic Assembly

Same

1000x Simpler & Cheaper

Faster & Cheaper

6/12/2019 | eLux PROPRIETARY | 13Micro LED Display Conference 2019Display

SWOT Analysis

Weaknesses

▪ eLux focus on 20 to 100 µm µLED is not suitable for small display

Opportunities

▪ µLED can replace LED displays over 32 ppi due to better performance and lower manufacturing cost

▪ µLED can replace OLED in high end displays due to better performance, long lifetime, and environmental stability

Threats

▪ Sony / Samsung have demonstrated µLED display since CES 2012

▪ Samsung, LG and many others are pursuing µLED display vigorously

▪ Time to market

eLux µLED

Strengths

▪ ~100% µLED utilization

▪ Moderate requirement for epi quality

▪ No mura due to randomizing

▪ Low fluidic assembly cost

▪ Active matrix ready

▪ IP (~40 patent families)


Summary

◼ eLux technology is positioned to enable µLED display for PID◼ The best µLED entry point is at 0.6 mm pitch where standard technology

fails

◼ 4K and 8K displays are 110”and 220” for retail and theater applications

◼ µLED display fluidic assembly has advantages over technologies◼ Randomize µLED in fluidic assembly prevents mosaic and non-uniform

illumination.

◼ Low cost of assembly tools and fast (low cost) process

◼ Able to use ~100% low cost epi wafers


Display

Thank You!

Technology and Latest Results on Fluidic Assembly of Micro ...

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